This invention relates to a backflow preventer.
Backflow preventers are principally to prevent contamination of a public water distribution system by reducing or eliminating backflow or back-siphonage of contaminated water into the system.
Usually, the backflow prevention assembly is installed in a pipeline between a main supply line and a service line that feeds an installation, e.g., a hotel, factory or other institution, or even a multiple or single family residence. A backflow prevention assembly typically includes two check valves that are configured to permit fluid flow only in the direction from the main supply line to the service line.
FIG. 1 illustrates a conventional connection between a valve module 40' and a housing 20' of a prior art backflow preventer. As shown, an annular mount 90 having an threaded inner surface 92 and a smooth outer surface 94 is secured to a cylindrical inner surface 96 of housing 20', e.g., by solder 98 or welding 99. The valve module 40' is then screwed into mount 90 to secure it to the housing.